1. Field of the Invention
This invention relates to a band grinding machine, particularly to one having a grinding-band swaying device possible to sway the grinding band of a band grinding machine for regularly changing grinding angles of the grinding band against a work in order to upgrade ground quality of a work.
2. Description of Prior Arts
A known conventional band-grinding machine shown in FIG. 1 includes a machine base 11, a worktable 12, a grinding-band wheelbase 13 and a motor 14. The worktable 12 is positioned on the machine base 11, with the grinding-band wheelbase 13 pivotally connected on the machine base 11. Further, two rollers 131 are positioned at the left side and the right side of the worktable 12, and an endless grinding band 132 extends around the two rollers 131. The motor 14 is fixed at the left side of the machine base just under the left roller 131 and connected with a swaying member 15, having its output end combined with the left roller 131 so as to drive the grinding band move around the two rollers 131. Further, an eccentric device 16 is provided to work with the motor 14, consisting of a main wheel 161 combined  with the motor 14, and an eccentric shaft 1611 fixed laterally on the main wheel 161, and a swaying shaft 162 pivotally connected with the eccentric shaft 1611. The swaying shaft 162 is firmly connected with the endless grinding band 13. Therefore, when the motor 14 rotates the main wheel 161, the eccentric shaft 1611 makes eccentric movement so that the grinding band 132 may sway laterally back and forth together with linear straight movement, caused by the stationary condition of the grinding-band wheelbase 13 and the swaying shaft 162.
However, the eccentric device 16 in the conventional band-grinding machine 10 has a disadvantage of a complicated structure, and the swaying shaft 162 has one end directly connected firmly with the band-grinding wheelbase 13. Then the main wheel 161 indirectly actuates the swaying shaft 162 via the eccentric shaft 1611, so the swaying shaft 162 may be interfered by the connected end with the grinding band wheelbase 13, resulting in unsmooth operation of the eccentric swaying. Moreover, the combining structure of the two ends of the swaying shaft 162 has to share the load of the motor 14 so the eccentric shaft 1611 may become gradually worn off by long-term usage, with the service life of the machine possible to be shortened. Further, an universal joint would have to be used for the connecting locations for the swaying shaft 162 and the  grinding-band wheelbase 13 and the eccentric shaft 1611, the structure should become quite complicated to end in high cost of the conventional band grinding machine.